Gluconeogenesis Flashcards
What is the effects of limited oxygen on metabolism
We will only undergo anaerobic glycolysis converting pyruvate into lactate,producing only 2 ATP
Glucagon signaling, no glycogen synthesis, fat breakdown, no oxidative phosphorylationthe PDC and CAC is slowed down
Lactate dehydrogenase converts nad back to NADH so can be used in glycolysis
Where does gluconeogenesis occur
In the liver And kidneys
What are the main substrates used in gluconeogenesis
Lactate and glycerol
Gluconeogenesis
Anabolic pathway that generates glucose from non-sugar molecules.it requires 4 different enzymes to overcome the 3 irreversible steps in glycolysis
Describe the 3 irreversible steps in gluconeogenesis
- Converting pyruvate to oxalacetate by adding a CO2 from bicarbonate using pyruvate carboxylase
- Decarboxylation of oxaloacetate producing pep and an unstable CO2
- Reverse step 3°F glycolysis reverting fructose 6 phosphate to glucose -6 - phosphate by a phosphatase
After the third irreversible step in gluconeogenesis, how is glucose 6 phosphate converted back to glucose
Glucose - 6-phosphatase hydrolyses G6P producing a glucose
What are the reactants and products of the reaction producing glucose from pyruvate
Reactants: 2 pyruvate, 4ATP,2 NADH, 2 GTP, 6 WATER
Products: 1 glucose, 4 ADP, 2 NAD+
How many glycerol molecules can be used to make a 6 carbon glucose
2 glycerol molecules- that contain three carbons each and enter the pathway as DHAP
How many ATP, NADH and water are produced/ consumed in the pathway that makes glucose from glycerol
2 ATPS and 2 waters are used, and 2 NADH are made
What is GNG important for
Supplying blood glucose
When is GNG activated
When we are exercising or fasting (during glucagon or epinephrine signaling)
What two amino acids can be used to produce glucose
Alanine > pyruvate in GNG
Aspartate> oxaloacetate in GNG
How does the liver know whether glycolysis or GNG is active?
When the body has a lot of ATP,acetyl coA (fats), Alanine (can be converted into pyruvate) the body will form more glucose and the process of converting pyruvate to oxaloacetate to PEP in GNG is on
When the body has a lot of ADP, GNG will turn off and Glycolysis will turn on along with AMP and F-1,6,BP.
Describe the allosteric regulation at step 3 for GNG and Glycolysis
High energy will inhibit PK1 preventing the formation of fructose 1-6 BP (in glycolysis)
F2 6 BP and AMP will inhibit F 1-6 BPtase in gluconeogensis preventing bisphosphate from reverting back to F6P
Low energy will inhibit GNG
Example of Reciprocal Regulation between GNG and Glycolysis
The formation of F2,6 BP will stimulate PFK-1, inhibiting GNG by inhibiting FBP-1 and activating Glycolysis.
What makes Fructose 2,6 bisphosphate
PFK-2 and FBPase 2 which are tandem enzymes that can hydrolyze or phosphorylate a molecule because it has two active sites can be reciprocally regulated via phosphorylation
What is the goal of reciprocal control in the liver
To allow either glycolysis or GNG to run and to ensure they do not operate at the same time
What happens when the PFK2- FBPase is phosphorylated? What does this mean for the metabolic pathways it affects?
When PFK 2/FBPase is phosphorylated, the PFK2 will be turned off and FBPase will be on, activating GNG because it can freely revert F2,6BP back to F6P
What happens when PFK2/FBPase 2 is dephosphorylated?
The FBPase is off and PFK 2 is on, glycolysis is more active because PFK-1 is activated allowing F6P to convert to F2,6BP
How are hormones integrated in this reciprocal regulation
Glucagon will activate PKA in fasting state, phosphorylating the enzyme complex.
Insulin will activate protein phosphatase 1 dephosphorylating the complex
What energy state will activate glycolysis
Low energy (ADP/AMP)
What energy state will turn on GNG
High energy
What is a marker for high blood glucose?Why?
Hemoglobin A1c.
Glucose can react with the valine on hemoglobin and this will prevent RBC turnover, making a lot of this molecule present in the body
